Mass and Heat Transfer Balance at Plasma-Liquid Interfaces

Abstract

Many of the discharge reactors involve direct interaction between the plasma and liquid media. Such interaction initiates many complex physical and chemical processes at the interface, which need to be well-understood for optimizing a discharge reactor for a specific application. While chemical processes such as reactive species transport across the interface received considerable interest in the literature, physical processes did not. In this work, a two-dimensional plasma numerical model is developed and is experimentally validated to analyze mass and heat transfer processes at a plasma-liquid interface, describing a pin-water reactor operating in air at atmospheric pressure. Preliminary results indicate that in the plasma side of the interface, the density of background gas drops to approximately 50% of its value under standard conditions due to gas rarefaction by the plasmas volumetric heating. Consequently, the energy of the ions bombarding the liquid increases, leading to steepening of the temperature gradient on the liquid side of the interface and surface vaporization. These findings indicate that the interface might be at a different temperature from both bulk phases, which has significant implications for species transport at the interface as the solubility of gaseous species in the liquid is a function of temperature.